Uncovering merging and joining as urban expansion processes

This paper focuses on the suitability of urban expansion in mountain areas against the background of accelerated urban development. Urbanization is accompanied by conflict and intense transformations of various landscapes, and is accompanied by social, economic, and ecological impacts. Evaluating the suitability of urban expansion (UE) and determining an appropriate scale is vital to solving urban environmental issues and realizing sustainable urban development. In mountain areas, the natural and social environments are different from those in the plains; the former is characterized by fragile ecology and proneness to geological disasters. Therefore, when evaluating the expansion of a mountain city, more factors need to be considered. Moreover, we need to follow the principle of harmony between nature and society according to the characteristics of mountain cities. Thus, when we evaluate the expansion of a mountain city, the key procedure is to establish a scientific evaluation system and explore the relationship between each evaluation factor and the urban expansion process. Taking Leshan (LS), China—a typical mountain city in the upper Yangtze River which has undergone rapid growth—as a case study, the logic minimum cumulative resistance (LMCR) model was applied to evaluate the suitability of UE and to simulate its direction and scale. The results revealed that: An evaluation system of resistance factors (ESRFs) was established according to the principle of natural and social harmony; the logic resistance surface (LRS) scientifically integrated multiple resistance factors based on the ESRF and a logic regression analysis. LRS objectively and effectively reflected the contribution and impact of each resistance factor to urban expansion. We found that landscape, geological hazards and GDP have had a great impact on urban expansion in LS. The expansion space of the mountain city is limited; the area of suitable expansion is only 23.5%, while the area which is unsuitable for expansion is 39.3%. In addition, it was found that setting up ecological barriers is an effective way to control unreasonable urban expansion in mountain cities. There is an obvious scale (grid size) effect in the evaluation of urban expansion in mountain cities; an evaluation of the suitable scale yielded the result of 90 m × 90 m. On this scale, taking the central district as the center, the urban expansion process will extend to the neighboring towns of Mianzhu, Suji, Juzi and Mouzi. Urban expansion should be controlled in terms of scale, especially in mountain cities. The most suitable urban size of LS is 132 km2.This would allow for high connectivity of urban-rural areas with the occupation of relatively few green spaces.

Modeling different urban growth patterns based on the evolution of urban form: A case study from Huangpi, Central China

The assessment of the land use / land cover expansion that occurred in the area over a period of thirty years is the utmost priority of this research work. Multi temporal Landsat satellite imageries TM 1984, 1990 and ETM+ 2002, 2014 from the United States Geological Survey (USGS) website were used as the primary dataset. Area of interest was clipped in ArcGIS 9.3 environment, image enhancement and image classification were adequately done using ENVI 4.5 remote sensing software. Using supervised classification algorithm, the images were classified into bare soil, built-up area, vegetation, water body and wetland; these were then used to carry out change detection analysis or time series analysis. Results obtained from the analysis of built-up area dynamics for the past three decades revealed that the town has been undergoing urban expansion processes. The expansion was prolonged both from urban centre to adjoining non-built-up areas in all directions. The total built up area in the town has expanded from 28.04sq/km in 1984 to 49.51 sq/km in 2014 at an average expansion rate of 0.7, 0.4 and 0.9 per annum during 1984 – 1990, 1990 – 2002 and 2002 – 2014 study periods respectively. The study period from 2002 – 2014 was the time at which the town experienced the highest urban expansion. The analysis of spatial trend revealed that the urban landscape has experienced a process of sprawling and fragmented development pattern particularly in the fringe areas while the town centre underwent infill and edge expansion development processes. The fringe areas show scattered expansion pattern. Quantifying urban expansion patterns and development processes of the past trends can help better understand the dynamics of built up area and guide sustainable urban development planning of the future urban growth.

Projections of urban built-up area expansion and urbanization sustainability in China's cities through 2030

PDF HTML阅读 XML下载 导出引用 引用提醒 沈阳经济区土地利用和净初级生产力变化 DOI: 10.5846/stxb201406061164 作者: 作者单位: 中国科学院沈阳应用生态研究所,中国科学院沈阳应用生态研究所,中国科学院沈阳应用生态研究所,辽宁省环境科学研究院,中国科学院沈阳应用生态研究所,中国科学院沈阳应用生态研究所,中国科学院沈阳应用生态研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41171155);辽宁省生态环境十年(2000-2010年)变化遥感调查与评估课题 Land use and net primary productivity changes in Shenyang Metropolitan Area Author: Affiliation: Institute of Applied Ecology,Chinese Academy of Sciences,Institute of Applied Ecology,Chinese Academy of Sciences,Institute of Applied Ecology,Chinese Academy of Sciences,Liaoning Academy of Environmental Sciences,Institute of Applied Ecology,Chinese Academy of Sciences,Institute of Applied Ecology,Chinese Academy of Sciences,Institute of Applied Ecology,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分析了沈阳经济区2000到2010年土地利用变化情况。基于CASA(Carnegie-Ames-Stanford Approach)模型估算2000年、2005年、2010年沈阳经济区净初级生产力(NPP),从行政区划和地类角度分析其时空变化,统计了不同地类转换模式下NPP的损益值,从土地利用变化探讨分析了沈阳经济区土地利用变化带来的NPP变化情况。结果表明:(1)农田,林地和城镇用地为研究区最主要土地利用类型。土地利用最显著变化是城镇用地扩张迅速,农田面积大量减少。林地面积有所减少,草地、湿地、裸地面积变化较小;(2)沈阳经济区NPP呈明显退化趋势,并且时空变化显著,2000到2005年退化幅度大于2005到2010年。除了阜新市有增加,其他市的NPP均为减少;(3)沈阳经济区6种土地利用类型的平均NPP都在下降,降幅最大的是林地。NPP损益分析表明农田转城镇带来的年均NPP损失最大。 Abstract:In recent decades, urban areas in China have been rapidly increasing. This urban area expansion has caused land use changes, which have enormous inuences on regional ecosystems. The potential environmental problems caused by urban expansion have attracted extensive attention from researchers. Net primary productivity (NPP) is the amount of solar energy converted to chemical energy through the process of photosynthesis. NPP loss may affect the composition of the atmosphere, fresh water availability, biodiversity, and the ecological adjusting mechanism of energy supply and distribution. Moreover, NPP is also an important ecosystem productivity indicator. Hence, studying the impact of land use changes, caused by urban expansion, on NPP is crucial to understanding ecosystem structure and function changes. In recent years, Shenyang Metropolitan Area has experienced rapid economic growth and industrial development under the guidance of the central government policy and local government strategy. As a result, urban area expansion of Shenyang Metropolitan Area has also accelerated, resulting in significant land use changes. The 10 years from 2000 to 2010 were representative of the process of Shenyang Metropolitan Area's urban expansion. This study analyzed land use changes with Shenyang Metropolitan Area from 2000 to 2010. Six categories of land use types were interpreted from Landsat TM/ETM remote sensing images: forestland, farmland, urban area, grassland, wetland, and bare land. NPP changes in the study area were estimated through the CASA model. The spatial and temporal dynamics of NPP were studied in regional and land use categorical scales. There is little prior research investigating this change trajectory of NPP under different land-use conversion types. The change of NPP caused by urban expansion of Shenyang Metropolitan Area was analyzed. The results showed: (1) Farmland, forestland, and urban areas were the main land use types within the study area. Rapid urban expansion and loss of farmland were the predominant land use changes. While the area of forestland decreased, grassland, wetland, and bare land area changed only slightly. The demand for land for urban construction was greater in 2005-2010 than the demand in 2000-2005; (2) The NPP of the study area decreased, and changed greatly both in spatial and temporal scales. The NPP decreased more rapidly in 2000-2005 than it did in 2005-2010. The NPP decreased in all of Shenyang Metropolitan Area, except for Fuxin City. The highest values of NPP reduction were in the eastern part of Shenyang Metropolitan Area and the lowest values were located in the northwest region of Shenyang Metropolitan Area; (3) The mean NPP in the six land use types declined. Forestland declined most rapidly and the conversion of farmland to urban area had the largest annual NPP loss. From 2000 to 2005, annual NPP loss from the conversion of farmland to urban area was 21886.68 tons/year. However, from 2005 to 2010, NPP declined to 7003.61 tons/year from the conversion of farmland to urban area. NPP loss was relatively high in the following conversion modes: forestland-farmland, forestland-urban area, and farmland-wetland. However, increases in NPP were observed in the conversions of wetland-grassland, wetland-bare land, and bare land-grassland. 参考文献 相似文献 引证文献

Urban expansion form is the most direct manifestation of urban expansion in space. Although it has been widely and vigorously studied, relatively little attention has been paid to reveal its spatiotemporal characteristics at the administrative level over a long timeframe. In this study, 31 Chinese municipalities and provincial capitals were selected as subjects to identify the urban expansion forms of provincial and higher level cities in China. First, urban expansion processes of these cities in the past four decades were reconstructed using remote sensing and geographical information system (GIS) technology. Then, the overall characteristics of urban expansion were presented to scientifically determine the urban expansion forms of the provincial and higher level cities in China. Afterwards, the annual expansion area per city (AEAC) index was employed to describe the urban expansion processes and determine the important time nodes of the 31 cities. Lastly, the urban expansion type (UET) index was adopted to analyze the spatiotemporal characteristics of urban expansion forms. Results indicate that (1) from the 1970s to 2013, urban lands in provincial and higher level cities in China expanded dramatically, with the central built-up area increasing by over 5 times, and urban expansion demonstrating an apparent spatial difference. The expansion rate of cities in East China was fastest with an AEAC of 13.78 km2, followed by that in Central China (AEAC = 9.67 km2). The urban expansion rate was slowest in West China (AEAC = 7.11 km2); (2) Affected by the national macro policies, urban expansion processes successively experienced four different stages: a slow expansion period (1970s–1987), an accelerating expansion period (1987–1995), a slowdown expansion period (1995–2000), and a high-speed fluctuating expansion period (after 2000); (3) The urban expansion forms of municipalities and provincial capitals were mainly edge-expansion supported by infilling expansion. The leapfrog form contributed minimally to urban expansion; (4) The edge-expansion form surged before 2010 and gradually slowed down after 2010. By contrast, infilling expansion kept increasing in the past four decades. Lastly, the rate of urban expansion via the leapfrog form fluctuated from the 1970s to 2013.

With the pursuit for global competitiveness and economic growth, Chinese cities have recorded massive urban land expansion. This article examines the effects of development policies and economic restructuring on urban land expansion in China through a case study of Nanjing, representing the rapidly growing and globalizing coastal cities in China. Wei investigate the development process and changing contents of government policies, and analyze development zones and key projects as privileged, trait making, and even path‐breaking elements of the development process. We highlight the transition and paradox of the Chinese state in the urban development process, and the broad contexts underlying urban land expansion in Chinese cities. We see urban expansion in China as a process largely responding to top‐down policy change and economic transition initiated by the central government. We hold that the role of the state has to be analyzed to understand urban transformation and land expansion, moving beyond local factors of accessibility and feasibility. Development‐zone and project fevers, and lagging administrative reforms, however, have made Chinese cities heavy with debt and led to wasteful development, corruption, and social unrest in China.

Spatio-temporal evolution of urban built-up areas and analysis of driving factors —A comparison of typical cities in north and south China

Land subsidence is a common urban geological disaster. With the acceleration of urbanization, land subsidence is increasingly affected by urban expansion. It is of great significance to study the influence of urban expansion on land subsidence for urbanization construction and policy guidance. Under the strategic background of building Beijing into a sub-center of the city, the rapid expansion of Tongzhou city, the accelerated construction of infrastructure and the sharp increase of population will all put new pressure on the evolution of land subsidence in Tongzhou. This paper takes Tongzhou District of Beijing as an example, and takes 2015-2021 as the research period. In order to reflect the increment of urban expansion process, the improved multilinear model and land use monitoring based on RS and GIS are used to study the urban expansion process, and the relationship between urban expansion and land subsidence in Tongzhou District is analyzed by using Sentinel-2 satellite remote sensing image data and GIS spatial analysis method. The results show that: 1) With the increase of years, the annual settlement in Tongzhou District of Beijing shows a slowing trend. 2) The process of urban expansion is accelerating, and the urban expansion shows a trend of first accelerating and then slowing down, which leads to the evolution of land subsidence in Tongzhou city. 3) There is a high correlation between the process of urban expansion and the trend of settlement.

In recent decades, rapid urbanization has occurred worldwide. During the COVID-19 pandemic, various countries implemented restrictions and lockdown policies that affected urban construction and expansion. However, detailed information about the impact of the pandemic on global urban expansion is lacking. Therefore, we selected 468 important cities worldwide and obtained quarterly time-series impervious surface maps for these cities during 2017−2022 without any labeled samples. To ensure the reliability of the analysis, 25 cities were excluded due to data limitations, resulting in a final sample of 443 cities. We then employed random forest regression models combined with SHAP analysis to quantify the relative importance of complex drivers of the urban expansion change rate, distinguishing between basic urban attributes and pandemic-related policies. Results show that 84% of 443 cities experienced a slowdown in urban expansion during the pandemic. We observe higher stability in high-urban-area group and high-population group and less stability in high-income group. At the country level, there were significant differences. Indonesia, Malaysia, and Germany experienced more pronounced slowdowns in the context of stringent policies, whereas China, India, Canada, and Spain presented milder deviations. In most cities, policy factors accounted for a greater proportion of feature importance than basic factors, and urban area and population groups characterized by a higher dominance of policy factors tended to exhibit a greater slowdown in urban expansion. SHAP analysis reveals a distinct policy divergence: internal health and movement regulations (e.g. facial coverings, vaccine availability, and stay-at-home requirements) were positively associated with urban expansion resilience, likely reflecting conditions that supported operational continuity by mitigating transmission risks. In contrast, external connectivity barriers (e.g. international travel controls), strict surveillance (e.g. contact tracing), and fiscal diversion (e.g. high income support scope) exhibited negative associations with urban expansion change rate. These observed patterns likely reflect barriers to the cross-border mobility of essential personnel and logistics, operational disruptions triggered by workforce isolation, and fiscal trade-offs diverting resources from infrastructure investment. This study reveals that in most cities, the infilling expansion proportion increased, while the outlying expansion proportion decreased during the pandemic. Notably, a higher proportion of outlying and edge expansion was associated with a mitigated reduction in urban expansion rates. This study provides insights for resilient and sustainable urban development, enabling improved responses to future pandemics and contributing to the United Nations Sustainable Development Goal 11.

Construction land expansion greatly affects the supply and interaction of distinct land use functions, particularly in rapidly urbanizing areas. However, existing research rarely focuses on the urban–rural gradient role of different construction land expansion processes in affecting the interactions between land use functions, which limits the refined high‐quality development of territorial space. Using the main urban area of Hangzhou as an example, this research analyzed the spatiotemporal transmission process of trade‐offs/synergies among distinct functions between urban and rural regions from the living‐production‐ecological function perspective, and probed the differences in the impact of distinct urban and rural construction land expansion processes on them across different urban–rural gradients, thereby proposing the urban–rural spatial development pathways for promoting synergistic territorial spatial patterns. The results showed that the changes in different functions had an obvious urban–rural gradient difference. During 2000–2020, the trade‐off between living function and other functions increased continuously, and regions with a higher trade‐off primarily shifted from urban development areas to urban–rural transition areas. The infilling and edge‐expansion of urban construction land were more favorable to the increased synergy between distinct functions; the infilling and edge‐expansion of rural construction land in urban development and urban–rural transition areas greatly reduced the functional trade‐off level, while its leapfrogging in rural development areas strongly affected the synergy between distinct functions. These findings can help to restrict unreasonable urban and rural construction land expansion processes as well as promote synergistic territorial space patterns in rapidly urbanizing regions.

Historical temperature records are often partially biased by the urban heat island (UHI) effect. However, the exact magnitude of these biases is an ongoing, controversial scientific question, especially in regions like China where urbanization has greatly increased in recent decades. Previous studies have mainly used statistical information and selected static population targets, or urban areas in a particular year, to classify urban-rural stations and estimate the influence of urbanization on observed warming trends. However, there is a lack of consideration for the dynamic processes of urbanization. The Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), and Pearl River Delta (PRD) are three major urban agglomerations in China which were selected to investigate the spatiotemporal heterogeneity of urban expansion effects on observed warming trends in this study. Based on remote sensing (RS) data, urban area expansion processes were taken into consideration and the relationship between urban expansion rates and warming trends was investigated using data from 975 meteorological stations throughout China. Although urban areas constitute less than 1% of land in China, more than 90% of the meteorological stations experienced urban land use change and the average urban expansion rate was 0.33%/a. There was also a significant positive relationship between observed warming trends and urban expansion rates. Background warming, without the influence of urbanization and extra warming induced by urbanization processes, was estimated using a linear regression model based on observed warming trends and urban expansion rates. On average, urbanization led to an additional annual warming of 0.034 ± 0.005 °C/10a. This urbanization warming effect was 0.050 ± 0.007 °C/10a for minimum temperatures and 0.008 ± 0.004 °C/10a for maximum temperatures. Moreover, it appeared that urbanization induced greater warming on the minimum temperature during the cold season and maximum temperature during the warm season.

Forty years of urban expansion in Beijing: What is the relative importance of physical, socioeconomic, and neighborhood factors?

The primary prerequisite for sustainable urban development is to accurately grasp the development of the city. The dynamic changes in the urban area can reflect the urban expansion process and spatial development model. Carrying out urban expansion monitoring and extracting urban areas is of great importance for grasping the law of urban development and promoting the sustainable development of cities. However, the related research reveals several problems such as insufficient accuracy and low intelligence of urban boundary extraction. In response to these problems, this paper proposes a new method for urban area extraction based on the progressive learning model. By combining prior knowledge and image features, the number of training samples required for machine learning is reduced, and the problem of using high-level semantic information expression in the process of urban areas is avoided by using the classification method, and thus the accuracy of urban area extraction is improved. The method uses urban road network data to divide the city into blocks. It applies the scene classification method to extract the urban areas and uses the pyramid layer-by-layer to carry out the space constraint method to integrate the urban extraction principle into the machine learning process, which can be obtained and kept artificial under a small sample condition. Extracting the effect of the urban area is very close, greatly reducing the workload and providing a new solution for high-precision automatic extraction of urban areas. Through the analysis of urban expansion, the following results were obtained: (1) from 2000 to 2015, China's provincial capital cities maintained a high-speed growth trend with a total area increased by 90%; (2) urban expansion showed significant regional differences. The eastern expansion rate gradually slowed down, the western and northeast regions accelerated their expansion, and the central region expanded steadily; (3) 61% of the provincial capital cities expanded exponentially; (4) the development of China's provincial capital cities was highly correlated with national urban development policies and regional development strategies.

Empirical studies of urban expansion have increased rapidly in recent decades worldwide. Previous studies mainly focused on cities in China, the United States or African countries, with Brazilian cities receiving less attention. Moreover, such studies are rare in purpose-built cities. Taking the urban expansion from scratch (1960) to urban agglomeration (2015) in the Federal District of Brazil (FDB) as an example, this study aims to quantify the magnitude, patterns, modes, types and efficiency of urban land expansion and attempts to reveal some implications within sustainable urban expansion thinking. Annual expansion, landscape metrics, local Moran’s I index, area weighted mean expansion index, and land-use efficiency were computed. The suitability of diffusion–coalescence theory and the impact of population growth and urban development policies on urban expansion were discussed. Urban land continuously expanded and became more fragmented during 1960–2015, which mainly occurred in SSW and WSW directions. Urban land evolved in a polycentric way. Edge expansion was identified as the stable contributor, and the importance of infilling and spontaneous growth alternated. Urban expansion in this region supported the diffusion–coalescence theory. Population growth promoted urban expansion, and the creation of peripheral urban nuclei and their development were associated with the urban expansion and the changes in urban land structure. This study adds new empirical evidence of urban expansion to Brazil urbanization, and compact urbanization, population control, and efficient urban land use should be considered in the future.